Acidic, neutral and alkaline cleaning compositions have been used for many years for removing soils such as grease, inorganic deposits and stains and the like from hard surfaces and the like. Acidic cleaning compositions are also efficient in the removal of limescale deposits from toilet bowls, baths, sinks and taps, provided that such cleaners are kept for sufficient time and in physical contact with the soil to be removed. Such deposits generally build up in instances where the water is hard. As calcium and magnesium salt deposits become caked onto these surfaces they become extremely difficult to remove.
And, too, the surfaces to which such cleaners may be applied are often vertical, inclined or irregularly shaped. Low viscosity liquid acidic cleaners may drip and sometimes run from such surfaces when applied thereto. As a result, the liquid acid cleaning composition may not have sufficient contact time or sufficiently close physical proximity with the surface and soil to work well or fully and thus fail to achieve the desired degree of removal of the limestone deposit or other soil. This presents a problem of inadequate cleaning.
In an effort to provide a solution to these liquid run-off and inadequate cleaning problems, rheology modifiers have been added to liquid acidic cleaners to thicken and give body to them. Increasing the viscosity of the cleaner enables it to be applied to the surface with reduced dripping and run-off so that the acid cleaner may have a longer contact time with the soiled surface being treated. The rheological properties of the resulting composition must also be such as to enable the cleaner composition to be filled into a bottle, trigger-pack or other suitably convenient container and thereafter to be applied to the soiled surface through an opening in the container, such as a spout, nozzle or spray device that facilitates uniform distribution onto easy-, moderate- and hard-to-reach surfaces. The rheological properties must also be such as to readily enable rinsing off the surface with water or wiping the surface with a sponge or cloth after the cleaning effect has been achieved so it is complete.
Some water-soluble polymers or hydrocolloids are useful as rheology modifiers in a wide variety of applications. These generally will hydrate and dissolve when dispersed in water to produce viscous solutions or gels. Illustrative but non-limiting types of hydrocolloid useful in this manner include natural polysaccharides, polysaccharide derivatives and synthetic polymers and the like. Specific non-limiting examples include guar gum, carob gum, carrageenan, alginate, carboxymethyl cellulose, hydroxyethyl cellulose and other cellulose derivatives, and polyacrylates. Biosynthetic gums are high molecular weight polysaccharides produced by the fermentation of a carbohydrate by a bacterium or other microorganism. In particular, these include the Xanthomonas as well as bacterial species of the genus Sphingomonas, Bacillus, Arthrobacter, Azotobacter, Klebsiella, Agrobacterium, Pseudomonas, Rhizobium and Sclerotium.
Xanthan gum is a biosynthetic gum produced by the fermentation of carbohydrate by a culture of Xanthomonas campestris. The fermentation process as well as the isolation and purification of the gum is set forth in U.S. Pat. No. 4,352,882 to Lucien G. Maury, which issued on Oct. 5, 1982, and U.S. Pat. No. 4,375,512 to Joe B. Richman, which issued on Mar. 1, 1983, each of which and both of which are hereby incorporated by reference in their entirety.
Xanthan gum is well known as a rheology modifier in a wide variety of applications. The rheological properties of xanthan gum in aqueous compositions, in particular its high degree of pseudoplastic shear-thinning character, make it well suited to applications in acidic cleaners. Under conditions of rest or low shear, an acidic cleaner containing xanthan gum exhibits a very high viscosity, thus giving effective surface adherence, resistance to run-off and suspension of any abrasive particles which may be incorporated in the cleaner. Under conditions of high shear, the cleaner exhibits a low viscosity, thus making it easy to fill into and apply from the container and easy to remove from the surface after the cleaning action has taken place.
Kelco Company Technical Bulletin I#20, published in February 1971, referred to the ability of xanthan gum, when incorporated in a wide range of cleaners from strong caustic types to acidic products, to impart the property of cling to inclined surfaces so that long contact time can be maintained.
U.S. Pat. No. 4,787,998, which issued to George K. Rennie and Paul D. Hardman on Nov. 29, 1988, discloses a fragrant liquid cleaning composition containing a shear-thinning polymer, such as xanthan gum, having viscosities within defined ranges at specific shear rates. That patent further discloses at column 1, lines 60-68 and column 2, lines 1-3 that:
The polymer should furthermore be compatible with the surface-active agents present in the cleaning composition. Suitable examples of polymers to be used according to the present invention are biopolymers such as the xanthan gums and derivatives thereof, such as Kelzan S, a partially acetylated xanthan gum ex Kelco Co., Shell-flo-XA ex Shell Chemicals Ltd, Enorflo-XA ex Shell Chemicals, Rhodapol ex Rhone-Poulence, cross-linked polyacrylates, such as Carbopol ex B. F. Goodrich Co. Ltd, succinoglucane, such as Shellflo-S ex Shell Chemicals Ltd, acrylic copolymers such as E.P. 1996 ex National Adhesives and Resins Ltd. PA1 The amount of polymer used in the cleaning composition generally ranges from 0.1-3.0%, usually from 0.25-1.0%, and preferably from 0.4-0.8 by weight. The liquid cleaning composition comprises furthermore as essential ingredients one or more detergent active materials which can be anionic, nonionic and zwitterionic type detergent actives or mixtures thereof. Usually anionic synthetic detergents, such as the alkylbenzene sulphonates, alkanesulphonates, alkylsulphates, alkylethersulphates or mixtures thereof can be used. PA1 A buffered thickening agent, for use in cleansing lotions or in topically applied medicaments or cosmetics, comprises a naturally occurring gum, such as a Xanthan gum, and an orthophosphate buffer. The buffer thus acts to increase the viscosity of the gum in use so that higher ionic concentrations can be tolerated without destabilisation of the emulsion when the buffered thickening agent is formed into a lotion. Preferably the buffered agent constitutes 0.5% to 2% by weight of an oil-in-water protective cleansing lotion which may also comprise 10% to 20% by weight of petrolatum. PA1 An acid cleaner and brightener concentrate composition comprising a dicarboxylic acid, an amine and water having a pH of about 1 to about 3 is useful in removal of tenacious soil, such as tarnish, discoloration, corrosion and oxidation products from vehicles, such as railroad rolling stock, without subsequent harm to surfaces, including coated polycarbonate glass substitute. PA1 The designation "xanthan gum" includes treated and modified materials, such as deacetylized xanthan gum, depyruvatized xanthan gum, xanthan gum cross-linked with polyvalent cations, the gum/glyoxal complexes, and the like. In the compositions of the invention, one gum or a mixture of gums may be used. It is known that within certain proportions, mixtures of gums possess a synergy in regard to viscosifying and/or gelling capability. Thus, synergism may be used to advantage in the compositions of the invention. PA1 The compositions may be prepared in any manner desired by mixing the various additives in water. It is desirable to initially disperse and dissolve the polysaccharide in water and then add the acid and finally the salt.
Further, that patent discloses at column 2, lines 4-13, that:
Research Disclosure RD-36417 published Feb. 16, 1994 discloses melamine resins, especially methylated melamine formaldehyde resins, are added to acid cleaners containing xanthan gum as the viscosifier in order to partially crosslink the gum and provide improved low shear rate viscosity over time. The resin is used in the range of 0.2-1.05 by weight of the acid cleaner, the effective level depending on the gum concentration and the type of acid.
United Kingdom Patent No. GB 2 182 339A to Avent Medical Limited, which published on May 13, 1987, discloses:
U.S. Pat. No. 3,993,575 to Joseph Howanitz et al., which issued on Nov. 23, 1976, discloses:
Although xanthan gum is well known as a rheology modifier in cleaners, characteristically the viscosity decreases undesirably over time at low pH, within about seven days after making the compositions. The extent to which the viscosity decreases is dependent on a number of factors, such as the pH and ionic strength of the cleaner and the pH levels, and the temperature of the acidic cleaner composition at which it is stored. In compositions stored at ambient temperature, xanthan gum loses a significant proportion, perhaps greater than about 20% or more, of its viscosifying functionality within an acidic composition in about seven days at a pH of about 2.2 or less. This may eventually lead to product performance disappointment and failure unless an increased concentration of xanthan gum is initially used to compensate for the decrease in viscosity. But this increased concentration may increase the production cost of the cleaner, and may render it more difficult to manufacture on account of the higher initial viscosity.
U.S. Pat. No. 4,302,253 to Peter A. Ciullo, which issued Nov. 24, 1981, discloses cleaning compositions consisting of a solution of mineral acid such as hydrochloric or formic acid thickened with a clay, xanthan gum and imidazoline. The imidazoline appears to function as an anti-flocculating agent for the clay and allegedly affords the composition some stability. However, the components may render the product cost sensitive.
U.S. Pat. No. 4,855,069 to Schuppiser et al., which issued Aug. 8, 1989, discloses aqueous acid compositions thickened by a polysaccharide for use particularly in the cleaning of surfaces. The compositions are stabilized against loss of viscosity during storage by the addition of a salt of a strong base and an acid having a pK equal or greater than 2. The stabilization results from an increase in the pH of the composition. It necessitates the incorporation of a significant quantity of an additional chemical, such as tri-sodium phosphate, in the cleaner. This has the disadvantages of increasing the production cost and environmental impact. This patent discloses at column 21, lines 49-59 that:
and further, column 3, lines 61-65 that:
Research Disclosure 36151 (May 1994, p. 271) discloses a process for producing a pre-degraded xanthan gum product which can be used for acid cleaner formulations where 100% viscosity stability is required. The process involves treatment of xanthan gum broth with hydrochloric acid. After a specified period, the broth is neutralized with a stoichiometric amount of sodium hydroxide and then pasteurized and further processed as normal. The disadvantage of this process is that the pre-degraded xanthan gum has a significantly reduced viscosifying ability and needs to be used at a relatively high concentration, thus increasing the production cost of the cleaner.
It would be advantageous if a xanthan gum product existed which had enhanced stability in acidic compositions over time. It would be advantageous if an acid cleaner could be formulated using xanthan gum at a concentration similar to that used in neutral pH cleaners of similar rheological properties, obviating the need to add another or other chemicals in order to stabilize the xanthan gum and composition against unacceptable decrease in viscosity during the shelf life of the acidic cleaning composition.